PC-1211, PC-1250, etc. TVM
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03-30-2021, 04:58 PM
Post: #1
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PC-1211, PC-1250, etc. TVM
In light of all the recent Sharp enthusiasm, here's my attempt at a TVM solver for the PC-1211, and compatible models like the PC-1250, and no doubt many others (and their corresponding Tandy/Radio Shack versions).
The math is based largely on the 17BII manual's formulas, this TVM program for serveral different HPs, and some of the mathematical notes found here. The PC-1211 and PC-1250 don't have hyperbolic functions for easy, accurate calculation of e^x-1 for |x| close to zero, but using the infinite series for ln(1+x) does offer some accuracy improvement. Usage is fairly straight-forward. On the PC-1211, you'll need to switch to DEF mode. On other models like the PC-1250, there's a dedicated DEF key that you press instead of Shift. Set B=1 for begin mode, otherwise set B=0. These are the key assignments - for storing variables, first enter the value into the display, then press the appropriate key: Shift Z: Store n Shift X: Store i% Shift C: Store PV Shift V: Store PMT Shift B: Store FV Shift A: Compute n Shift S: Compute i% Shift D: Compute PV Shift F: Compute PMT Shift G: Compute FV Code: 1 "Z":AREAD N Results are generally pretty good, and don't seem to differ by more than a few thousandths of a penny in the few sample problems that I tried. I'm not sure if the Sharps use binary rather than decimal, but I did notice that solving for PMT in a problem where FV=0, then immediately solving for FV could yield small non-zero values on the order of 1E-5. |
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